Process of preparing discotic liquid crystalline compounds

ABSTRACT

The invention relates to a process of preparing a discotic liquid crystalline compound by intramolecular oxidative cyclisation of a diaryl compound in an organic solvent in the presence of a strong acid, characterized in that an oxidative agent comprising a chrom(VI)oxide derivative is used, to discotic liquid crystalline compounds obtainable from said process, to liquid crystalline media, (co)polymers or polymer networks with columnar phases comprising said discotic liquid crystalline compounds, and to the use of said discotic liquid crystalline compounds, liquid crystalline media or liquid crystalline (co)polymers with columnar phases for liquid crystal displays, optical elements like polarizers, compensators or colour filters, chemical sensors, charge transport materials, optical storage media, nonlinear optics, decorative pigments, adhesive or synthetic resins with anisotropic mechanical properties.

The invention relates to a process of preparing a discotic liquidcrystalline compound by intramolecular oxidative cyclisation of a diarylcompound in an organic solvent in the presence of a strong acid,characterized in that an oxidative agent comprising a chrom(VI)oxidederivative is used.

The invention further relates to discotic liquid crystalline compoundsobtainable by the above process and to the use of said discotic liquidcrystalline compounds in liquid crystalline media with columnar phasesand in the preparation of liquid crystalline (co)polymers or polymernetworks.

The invention also relates to liquid crystalline media and liquidcrystalline (co)polymers comprising inventive discotic liquidcrystalline compounds, and to the use of inventive discotic liquidcrystalline compounds, liquid crystalline media or liquid crystallinepolymers for liquid crystal displays, optical elements like polarizers,compensators or colour filters, chemical sensors, charge transportmaterials, optical storage media, nonlinear optics, decorative pigments,adhesives or synthetic resins with anisotropic mechanical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show the X-ray diffraction pattern of two samples of aninventive discotic liquid crystalline compound according to example 2.

FIGS. 2A and 2B show an inventive discotic liquid crystalline compoundaccording to example 2 between crossed nicol polarizers upon applicationof an electric field.

FIGS. 3A to 3D show the X-ray diffraction pattern of samples of aninventive discotic liquid crystalline elastomer according to example 3.

FIG. 3E shows the azimuthal intensity distribution of the diffractionpattern of FIG. 3A.

FIGS. 4A and 4B show the X-ray diffraction pattern of samples of aninventive discotic liquid crystalline elastomer according to example 3.

FIGS. 4C and 4D show the azimuthal intensity distribution of thediffraction pattern of FIG. 4A in horizontal and vertical directionsrespectively.

DETAILED DESCRIPTION OF THE INVENTION

Most of the liquid crystalline compounds and mixtures that are nowadayscommercially used comprise calamitic, i.e. rod-shaped, moieties, whereasdiscotic, i.e. disk-shaped liquid crystalline compounds have hithertofound only limited applications.

Discotic liquid crystalline compounds exhibit columnar discotic ordiscotic nematic phases. Of these, especially the columnar phase hasattracted commercial interest. In the columnar phase the disk-shapedmolecules are stacked in columns that are laterally arranged in a twodimensional lattice. This leads to specific anisotropic properties ofthe columnar phase, such as e.g. anisotropic charge transportproperties, which can be used in various applications.

Discotic liquid crystalline compounds, in particular discotictriphenylenes, have been proposed as charge transport and/orphotosensitive materials for optical information storage, chemicalsensors, photocopiers or laser printers (DE 43 39 711), light emittingdiodes and electroluminescent displays (DE 43 43 412) or opticallyuniaxial negative compensation films (EP 0 646 829).

Most of the discotic liquid crystalline compounds described in prior artare triphenylene derivatives. Recently, however, it has been shown by G.Scherowsky and X. H. Chen, Liq Cryst. 17, 803 (1994) that phenanthrenesalso exhibit columnar phases when being substituted by six aliphaticalkylcarbonyloxy chains. The DE 43 07 049 discloseshexaoctanoyloxyphenanthrenes that exhibit a columnar discotic phase.

On the other hand, hexaalkoxyphenanthrenes, which are also covered bythe generic formula of the DE 43 07 049 but not specifically disclosedtherein, have been reported by X. H. Chen, PhD thesis, TU Berlin (1994)to melt directly from the crystalline state to the isotropic state,without transiting via the columnar mesophase.

The phenanthrenes as disclosed in the DE 43 07 049 are prepared byphotocyclisation of the corresponding stilbenes via irradiation with UVlight. However, this method gives generally poor yields and is suitableonly for synthesis at small scale.

A. J. Liepa and R. E. Summons, J. Chem. Soc. Chem. Comm. 826 (1977)reported the conversion of stilbenes into phenanthrenes by oxidativecyclisation in the presence of vanadium oxytrifluoride (VOF₃) in anacidic medium. However, besides other disadvantages this method is notsuitable for large scale production, since the reagent VOF₃ is ratherexpensive.

Thus, there is still a demand for a method to synthesize discotic liquidcrystalline compounds, in particular discotic phenanthrenes, that show acolumnar discotic phase and can be obtained at large scale and in highyields.

The inventors have now found that discotic phenanthrene derivatives canbe synthesized in high amounts by oxidative cyclisation ofcyanostilbenes in an organic solvent in the presence of a pyridinecomplex of a chrom(VI)oxide derivative, in particularpyridinchlorochromate (PCC), and a strong acid, like e.g. borontrifluoride or trifluoroacetic acid. This method not only gives highyields, but is also suitable for large scale production.

Derivatives of chrom(VI)oxide and their organic complexes like e.g.chromic acid-pyridine complex, 2,2′-bipyridyl-chrom(VI)oxide complex,pyridinchloro- or fluorochromate (PCC, PFC) or pyridindichromate (PDC),are used in prior art in organic synthesis for the oxidativetransformation from alcohols to aldehydes or ketones, as described e.g.in Houben-Weyl, Methoden der organischen Chemie Volume E3 (“Aldehydes”),Thieme-Verlag (Stuttgart). However, until now no example ofintramolecular coupling between aromatic nuclei on using PCC has beenreported in prior art.

One aim of the present invention is to provide discotic liquidcrystalline compounds and methods for their preparation that do not bearthe disadvantages of the compounds and methods of prior art as discussedabove. Another aim of the present invention is to provide newpolymerizable discotic liquid crystalline compounds and polymers,elastomers and polymer networks obtained from them. Another aim of thepresent invention is to extend the pool of discotic liquid crystallinematerials available to the expert. Other aims of the invention areimmediately evident to a person skilled in the art from the followingdescription.

It has been found that the above mentioned aims can be achieved and thedrawbacks of prior art can be overcome by providing discotic liquidcrystalline compounds and a method to synthesize these compounds asdescribed in this invention.

One object of the present invention is a process of preparing a discoticliquid crystalline compound by intramolecular oxidative cyclisation of adiaryl compound in an organic solvent in the presence of a strong acid,characterized in that an oxidative agent comprising a chrom(VI)oxidederivative is used.

Another object of the present invention is a process as described aboveof preparing a discotic liquid crystalline compound of formula I

by intramolecular oxidative cyclisation of a diaryl compound of formulaIa

wherein

A is an aliphatic or aromatic five- or six-membered ring,

Y is —CH₂—, —NH—, —CH═CW—, —CO—, —COO—, or a radical >CH—CH< or >C═C<that is part of a mono- or bicyclic group comprising one or twocondensated five- or six-membered aromatic or aliphatic rings, each ofwhich may comprise one or more hetero atoms and may be unsubstituted,mono- or polysubstituted by R¹,

W is halogen, a dipolar group preferably selected from CN, NO₂, SO₂CH₃,SOCH₃, SOCF₃, SOOCH₃, SOOCF₃ or COR¹, or has one of the meanings of R¹,

R¹ to R⁶ are in each case independently H, straight-chain or branchedalkyl with 1 to 15 C atoms which may be unsubstituted, mono- orpolysubstituted by halogen or CN, it being also possible for one or morenon-adjacent CH₂ groups to be replaced, in each case independently fromone another, by —O—, —S—, —NH—, —N(CH₃)—, —CH(OH)—, —CO—, —COO—, —OCO—,—OCO—O—, —S—CO—, —CO—S—, —CH═CH— or —C≡C— in such a manner that oxygenatoms are not linked directly to one another, or alternatively one ormore of R¹ to R⁶ are denoting P—(Sp—X)_(n)—,

P is a polymerizable group,

Sp is a spacer group having 1 to 15 C atoms,

X is group selected from —O—, —S—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—,—CO—S— or a single bond, and

n is 0 or 1.

In a preferred embodiment of the present invention, the oxidative agentin the inventive process is a pyridinium complex or complex salt of achrom(VI)oxide derivative, in particular pyridiniumchlorochromate (PCC).

In another preferred embodiment, boron trifluoride etherate ortrifluoroacetic acid is used as strong acid in the inventive process.

A preferred embodiment of the present invention is a process ofpreparing a discotic liquid crystalline phenanthrene derivative offormula II

by intramolecular oxidative cyclisation of a stilbene derivative offormula IIa

wherein W and R¹ to R⁶ have each independently one of the meanings offormula I.

Further preferred embodiments relate to a process of preparing discoticliquid crystalline compounds of formula II, wherein

W is —CN, —CHO or P—(Sp—X)_(n),

at least two of R¹ to R⁶ are each independently denoting straight-chainor branched alkoxy or alkenyloxy with 1 to 12 C atoms,

at least one of R¹ to R⁶ is denoting P—(Sp—X)_(n),

P is a vinyl, vinyloxy, acrylate, methacrylate, chloroacrylate, epoxy orstyrene group.

Another preferred embodiment of the present invention is a process ofpreparing a discotic liquid crystalline phenanthrene derivative offormula II by reacting the benzaldehyde IIb*

with the benzylcyanide IIc*

wherein R¹* to R⁶* have one of the meanings of R¹ in formula I, in thepresence of a base to the cyanostilbene IIa*,

followed by intramolecular oxidative cyclisation of the cyanostilbeneIIa* in an organic solvent in the presence of PCC and a strong acid togive the phenanthrene II*,

and optionally converting one or more of the groups R¹* to R⁶* and/orthe nitrile group of the phenanthrene II* by known methods into thedesired substituents to give a phenanthrene derivative of formula II.

Particularly preferred is a process as described above wherein R²*, R³*,R⁴* and R⁵* are straight-chain or branched alkoxy or alkenyloxy with 1to 12 C atoms.

Another object of the invention are discotic liquid crystallinecompounds obtainable by a process as described in the foregoing and thefollowing.

The formulae shown above and below embrace both known and new discoticliquid crystalline compounds. The new and preferred discotic liquidcrystalline compounds as described above and below, in particular thenew and preferred phenanthrene compounds, compounds of formula I and IIand their subformulae, and polymerizable discotic compounds are anotherobject of the present invention, independently of the method of theirpreparation.

Another object of the invention is the use of discotic liquidcrystalline compounds prepared by the inventive process in liquidcrystalline media with columnar phases and for the preparation of liquidcrystalline (co)polymers, elastomers, polymer gels or polymer networks.

Further objects are liquid crystalline media with a columnar phasecomprising at least two components, at least one of which is a discoticliquid crystalline compound as described in the foregoing and thefollowing, and liquid crystalline polymers obtainable from discoticliquid crystalline compounds as described in the foregoing and thefollowing by polymerization or polymeranaloguous reaction.

Yet another object of the invention is the use of inventive discoticliquid crystalline compounds, liquid crystalline media or liquidcrystalline (co)polymers as described in the foregoing and the followingfor liquid crystal displays, optical elements like polarizers,compensators or colour filters, charge transport materials, opticalstorage media, nonlinear optics, decorative pigments, adhesives orsynthetic resins with anisotropic mechanical properties.

Of the compounds of formula I and II especially preferred are thosewherein W is CN, F, Cl, CHO or P—(Sp—X)_(n)—, in particular CN or CHO,very preferably CN. Further preferred are those wherein W is an alkylgroup with 1 to 12 C atoms wherein at least one CH₂ group is replaced by—CO—.

Further preferred are compounds wherein at least one of the groups R¹ toR⁶ is an achiral alkyl radical which is unsubstituted or substituted byat least one halogen atom, it being possible for one or two non—adjacentCH₂ groups of these radicals to be replaced by —O—, —S—, —CO—, O—CO—,—CO—O— or —O—CO—O— groups.

Halogen is preferably F or Cl.

If W or one or more of R¹ to R⁶ are an alkyl or alkoxy radical, i.e.where the terminal CH₂ group is replaced by —O—, this may bestraight-chain or branched. It is preferably straight-chain, has 2, 3,4, 5, 6, 7 or 8 carbon atoms and accordingly is preferably ethyl,propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy,pentoxy, hexoxy, heptoxy, or octoxy, furthermore methyl, nonyl, decyl,undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, nonoxy,decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy, for example.

Oxaalkyl, i.e. where one CH₂ group is replaced by —O—, is preferablystraight-chain 2-oxapropyl (═methoxymethyl), 2-(═ethoxymethyl) or3-oxabutyl (═2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-, or5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-,6-,7-, 9-oxadecyl, for example.

A further preferred meaning for W and R¹ to R⁶ is alkenyl, i.e. alkylwherein one or more CH₂ groups are replaced by —CH═CH—. It is preferablystraight chain or branched alkenyl with 2 to 7 C atoms. Straight chainalkenyl groups are preferred. Further preferred alkenyl groups areC₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl, C₅-C₇-4-alkenyl, C₆-C₇-5-alkenyl andC₇-6-alkenyl, in particular C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl andC₅-C₇-4-alkenyl.

Of these, especially preferred alkenyl groups are vinyl, 1E-propenyl,1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl,3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z,hexenyl,4E-hexenyl, 4Z-heptenyl, 5-hexenyl and 6-heptenyl. Alkenyl groups withup to 5 C atoms are particularly preferred.

W and R¹ to R⁶ may be achiral or chiral groups. In case of achiralgroups they have preferably one of the preferred meanings given above.In case of chiral groups they are preferably selected according to thefollowing formula IV:

wherein

X¹ has the meaning given for X,

Q¹ is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a singlebond,

Q² is an alkyl or alkoxy group with 1 to 10 C atoms which may beunsubstituted₁ mono- or polysubstituted by halogen or CN, it being alsopossible for one or more non-adjacent CH₂ groups to be replaced, in eachcase independently from one another, by —C—═C—, —O—, —S—, —NH—,—N(CH₃)—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO— or —CO—S— in such a mannerthat oxygen atoms are not linked directly to one another, oralternatively has the meaning given for P—Sp—,

Q³ is halogen, a cyano group or an alkyl or alkoxy group with 1 to 4 Catoms different from Q².

Preferred chiral groups are 2-butyl (=1-methylpropyl), 2-methylbutyl,2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2-octyl,in particular 2-methylbutyl, 2-methylbutoxy, 2-methylpentoxy,3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 2-octyloxy,2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-nonyl,2-decyl, 2-dodecyl, 6-methoxyoctoxy, 6-methyloctoxy,6-methyloctanoyloxy, 5-methylheptyloxycarbonyl, 2-methylbutyryloxy,3-methylvaleroyloxy, 4-methylhexanoyloxy, 2-chlorpropionyloxy,2-chloro-3-methylbutyryloxy, 2-chloro-4-methylvaleryloxy,2-chloro-3-methylvaleryloxy, 2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl,1-methoxypropyl-2-oxy, 1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy,1-butoxypropyl-2-oxy, 2-fluorooctyloxy, 2-fluorodecyloxy, for example.

In addition, compounds of the formula I and II wherein one or more of Wand R¹ to R⁶ are denoting an achiral branched group may occasionally beof importance as co-compounds, for example, due to a reduction in thetendency towards crystallization. Branched groups of this type generallydo not contain more than one chain branch. Preferred achiral branchedgroups are isopropyl, isobutyl (=methylpropyl), isopentyl(=3-methylbutyl), isopropoxy, 2-methylpropoxy and 3-methylbutoxy.

Compounds of formula I and II are preferred wherein R⁶ is H and R¹ to R⁵have one of the preferred meanings given above. Particularly preferredare compounds wherein one or more, preferably two to five, in particularfour or five of the groups R¹ to R⁶ are denoting straight-chain orbranched alkoxy with 1 to 12, preferably 1 to 8 C atoms. Veryparticularly preferred are compounds wherein R⁶ is H and R², R³, R⁴ andR⁵ are alkoxy or alkenyloxy with 1 to 12, preferably 1 to 8 C atoms.

Further preferred are compounds wherein R¹ to R³ and/or R⁴ and R⁵respectively have the same meaning.

The polymerizable group P is preferably vinyl, vinyloxy, acrylate,methacrylate or epoxy group. Especially preferably P is vinyl, vinyloxy,acrylate or methacrylate, in particular vinyl or acrylate.

Particularly preferred are compounds of formula I and II comprising onepolymerizable group. Further preferred are compounds having two to six,especially two to five, in particular two or three polymerizable groups.In particular preferred are compounds wherein W is cyano and one or moreof R¹ to R⁶ are carrying a polymerizable group.

As for the spacer group Sp all groups can be used that are known forthis purpose to the skilled in the art. The spacer group Sp ispreferably linked to the polymerizable group P by an ester or ethergroup or a single bond. The spacer group Sp is preferably a linear orbranched alkylene group having 1 to 20 C atoms, in particular 1 to 12 Catoms, in which, in addition, one or more, non-adjacent CH₂ groups maybe replaced by —O—, —S—, —NH—, —N(CH₃)—, —CO—, —O—CO—, —S—CO—, —O—COO—,—CO—S—, —CO—O—, —CH(halogen)—, —CH(CN)—, —CH═CH— or —C≡C—.

Typical spacer groups Sp are for example —(CH₂)_(o)—,—(CH₂CH₂O)_(r)—CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂— or —CH₂CH₂—NH—CH₂CH₂—, with obeing an integer from 2 to 12 and r being an integer from 1 to 3.

Preferred spacer groups Sp are ethylene, propylene, butylene, pentylene,hexylene, heptylene, octylene, nonylene, decylene, undecylene,dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene,ethylene-thioethylene, ethylene-N-methyl-iminoethylene and1-methylalkylene, for example.

In a preferred embodiment of the invention the compounds of formula Iand II comprise a spacer group Sp that is a chiral group of the formulaV:

wherein

Q¹ and Q³ have the meanings given in formula IV, and

Q⁴ is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a singlebond, being different from Q¹.

Further preferred chiral spacer groups are chiral groups based onnaturally available materials, such as e.g. citronellol or lactatederivatives.

In particular preferred are polymerizable compounds wherein n is 1.

Another preferred embodiment relates to mixtures of polymerizablecompounds wherein n is 0 and polymerizable compounds wherein n is 1.

In the event that one or more of the groups W and R¹ to R⁶ are denotingP—Sp—X—, the spacer groups may be identical or different

In the inventive process, derivatives of chrom(VI)oxide or theircomplexes or complex salts are used as oxidative agent. These reactantsare known in the oxidation of alcohols to aldehydes or ketones, and aredescribed e.g. in Houben-Weyl, Methoden der organischen Chemie, 4^(th)Edition, Volume E3 (Aldehydes), Page 290 ff (Thieme-Verlag, Stuttgart1985).

The oxidative agent in the inventive process is preferably a complex ofa chrom(VI)oxide derivative, such as chromic acid or halogeno-chromate,with an organic compound, like pyridine or 3,5-dimethylpyrazole, inparticular a pyridine complex It is preferably selected from the groupcomprising chromic acid-pyridine complex, 2,2′-bipyridyl-chrom(VI)oxidecomplex, pyridinchloro- or fluorochromate (PCC, PFC) orpyridindichromate (PDC), and is particularly preferably PCC or PFC, verypreferably PCC.

The intramolecular oxidative cyclisation according to the inventiveprocess is carried out in an organic solvent. Polar solvents, like e.g.dichloromethane, chloroform or CCl₄, or non-polar solvents, like e.g.hydrocarbons such as petrolether or cyclohexane can be used. Preferablya polar solvent is used, in particular dichioromethane or chloroform.

The cyclisation reaction is carried out in the presence of a strongacid. Particularly preferred are strong lewis-acids, like e.g. borontrihalogenides and their complexes or perhalogenated organic acids, likee.g. perfluorocarboxylic acids. Particularly preferred are borontrifluoride etherate or trifluoroacetic acid, very preferably borontrifluoride etherate.

The temperature at which the cyclisation reaction is carried out ispreferably within the range from −80° C. to +30° C., in particular from−30° C. to +25° C., very preferably from 0° C. to +20° C.

The selection of the optimum reaction conditions, such as the reactionparameters like e.g. the temperature or the components of the reactionmixture like e.g. the solvent and the acid, is also depending on thespecific type of educts used. It is further depending on the otherparameters of the reaction conditions and the individual components ofthe reaction mixture. Thus, the optimum conditions can be selected ineach case independently by the expert from the preferred compounds andranges mentioned above, in order to adapt them to the synthesis of thedesired inventive compounds at high yields.

The discotic liquid crystalline compounds obtained by the inventiveprocess can be further modified by transforming the substituents W, R¹to R⁶ and R¹* to R⁶* to give the compounds of formula I and II.

It is further possible to introduce the desired substituents into thearomatic rings of the compounds of formula Ia, IIa and IIa* prior to thecyclisation reaction. This can be done e.g. by transforming thesubstituents R¹ to R⁶ and R¹* to R⁶* prior to or after the synthesis ofthe compounds of formula Ia, IIa and IIa* and/or by selecting thesecompounds or their educts accordingly.

For example, after the preparation of the cyanophenanthrene (II*) asdescribed above and below it is possible to transform the cyano group byesterification or etherification into the desired substituent.

It is also possible to introduce one or more substituents with aterminal polymerizable group to the aromatic core prior to or after thecyclisation reaction. Thereby polymerizable compounds of formula I andII can be prepared. These can be used for the preparation of liquidcrystalline polymers with columnar discotic phases.

The transformation or introduction of specific substituents as describedabove can be carried out by the expert without further elaboration byusing known methods.

In the following, the inventive process is exemplarily described indetail for a particularly preferred embodiment, wherein a cyanostilbeneof formula (IIa*) is prepared by reacting a substituted benzaldehyde offormula (IIb*) with a substituted benzyicyanide of formula (IIc*) in thepresence of a base. The cyanostilbene (IIa*) is then converted into thephenanthrene (II*) by intramolecular oxidative cyclisation in an organicsolvent with PCC as oxidative agent in the presence of a strong acid.

As mentioned above, the methods of preparation of discotic liquidcrystalline phenanthrenes reported in prior art bear severaldisadvantages. Thus, the method described in the DE 43 07 049 viaphotocyclisation of the corresponding stilbenes by irradiation with UVlight gives poor yields and is suitable only for synthesis at smallscale.

The method reported by A. J. Liepa and R. E. Summons, J. Chem. Soc.Chem. Comm. 826 (1977) via oxidative cyclisation of stilbenes in thepresence of VOF₃ in an acidic medium, although giving acceptable yields,is also not suitable for large scale production due to the use of theexpensive reagent VOF₃.

In contrast to this, the synthesis of discotic liquid crystallinephenanthrenes according to the inventive method not only gives higheryields but is also suitable for large scale production.

Thus, PCC is about 10 to 20 times less expensive than VOF₃ and theoxidative cyclisation requires only two mole equivalents of PCC, whilefour mole equivalents of VOF₃ are needed.

In addition, it could be shown by the inventors for the preparation ofhexamethoxyphenanthrenes that, when increasing the number of methoxygroups on the phenanthrene core, the yield of the oxidation reactiondecreases strongly when VOF₃ is used, while still being high when PCC isused as oxidant.

This is a particular advantage of the inventive method, as it gives wayto the synthesis of a broad variety of up to hexasubstitutedphenanthrenes with still high yields. This is suitable for example whenthe liquid crystalline properties of the inventive compounds areoptimized by changing the pattern of substitution of the aromatic rings,or when polymerizable compounds are prepared.

Another drawback of the method using VOF₃ is that the phenanthrenesundergo rapid decomposition in the acidic reaction medium when thereaction time, e.g. in an attempt to increase the yield, is prolonged bymore than 10 to 15 minutes.

More specifically, the compounds of formula I and II can be prepared andtheir substituents be transformed according to or in analogy to thefollowing reaction schemes.

wherein R′ and R″ have one of the meanings of R¹ in formula I, R¹ to R⁶have the meaning of formula I, Hal is halogen and m is an integer from1to 12.

Further to the methods described above, the substituents R and R¹ to R⁶in the compounds of formula I and II can be converted into the desiredgroups prior to or after the cyclisation reaction by methods which areknown per se and which are described, for example, in standard works oforganic chemistry such as, for example, Houben-Weyl, Methoden derorganischen Chemie, Thieme-Verlag, Stuttgart. Some specific methods ofpreparation can be taken from the examples.

Apart from the preparation of compounds of phenanthrenes of formula IIas described above, it is also possible to prepare the followingdiscotic compounds with the inventive process

wherein the aromatic rings in the compounds I-1 to I-4 and I-1a to I-4amay also be mono- or polysubstituted by R¹ to R⁶, and the centralphenylene ring in compound I-4a and the corresponding ring in compoundI-4 may also be connected via neighboured C atoms to another five- orsix-membered aliphatic or aromatic ring which may also comprise one ormore hetero atoms to form a condensated bicyclic system.

The skilled in the art can easily choose the specific reactants andconditions in order to adapt the inventive process as described for thepreferred embodiments above to the synthesis of the compounds I-1 toI-4.

It is also possible to synthesize crosslinked polymers or polymer gels,e.g. by polymerization of mixtures comprising compounds of formula Iand/or II in the presence of crosslinking agents, or by polymerizationof mixtures comprising compounds of formula I and/or II wherein two ormore of the radicals W and R¹ to R⁶ are bearing a polymerizable group.

Depending on the content of compounds with more than one polymerizablegroup (multifunctional compounds) in the polymerizable mixture, thecrosslink density is varied. When small amounts of multifunctionalcompounds are used, liquid crystalline elastomers are obtained, whereasin the presence of high amounts of multifunctional compounds liquidcrystalline duromers are obtained.

In particular densely crosslinked polymers show very high thermalstability of the optical and mechanical properties compared to linearpolymers.

Liquid crystalline polymers can be prepared from the inventive discoticcompounds e.g. by radicalic, cationic or anionic polymerization ofcompounds of formula I or II wherein at least one of W and R¹ to R⁶ iscomprising a terminal vinyl, vinyloxy, acrylate, methacrylate,chloroacrylate, epoxy or styrene group.

Polymerization can be carried out e.g. by solution polymerization or byin-situ polymerization. Radicalic solution polymerization can be carriedout for example in a solvent like dichloromethane, tetrahydrofuran ortoluene using AIBN as an initiator and heating for 24 hours at 30 to 60°C.

In order to obtain polymers with macroscopic uniform orientation, theliquid crystalline polymers prepared by solution polymerization can besubsequently aligned e.g. by uniaxial shearing and/or by applyingspecial means like electric or magnetic fields and high temperatures.

A particularly suitable method to prepare liquid crystalline polymerswith uniform orientation is by in-situ polymerization of polymerizableinventive compounds or polymerizable mixtures comprising the inventivecompounds in their liquid crystalline phase. In-situ polymerization canbe carried out e.g. by irradiation of the polymerizable material with UVlight in the presence of a UV-photoinitiator, like for example thecommercially available Irgacure 651 (from Ciba Geigy AG).

According to this method, the polymerizable material is coated as a thinlayer onto a substrate, aligned in its liquid crystalline phase byconventional techniques and cured by exposure to UV light to fix thealignment. A detailed description of this method can be found in D. J.Broer et al., Makromol.Chem. 190, 2255ff. and 3202ff. (1989).

In addition to light- or temperature-sensitive initiators thepolymerizable mixture may also comprise one or more other suitablecomponents such as, for example, crosslinking agents, catalysts,stabilizers, co-reacting monomers or surface-active compounds.

As substrates for example glass plates or plastic films can be used. Toachieve uniform alignment, the films can be sheared for example by meansof a doctor's blade. In some embodiments it may be of advantage to applya second substrate in order to exclude water or oxygen that may inhibitthe polymerization. Alternatively the curing can be carried out under anatmosphere of inert gas.

Another method to prepare liquid crystalline polymers from the inventivediscotic compounds is by polymeranaloguous reaction. For example,compounds of formula I and II carrying terminal C—C-double bonds can beadded to a polyhydrogensiloxane chain by hydrosilylation reaction in thepresence of a catalyst, like e.g. the commercially available Pt catalystSLM 86005 (from Wacker Chemie, Germany).

Crosslinked polymers, such as elastomers or densely crosslinked polymernetworks can be obtained by the above hydrosilylation reaction ofcompounds of formula I and II comprising two or more substituents with aterminal double bond, or by using e.g. divinyl compounds ascrosslinkers.

It is also possible to prepare liquid crystalline elastomers with achemically permanent director alignment via a two-step crosslinkingprocess as described e.g. by J. Küpfer, H. Finkelmann inMakromol.Chem.Rap.Comm.12, 717-726 (1991). According to this method, ina first crosslinking step a slightly crosslinked elastomer is prepared.This elastomer is subjected to uniaxial deformation as a result of whichthe director is macroscopically aligned in a uniform orientation. Theuniform orientation is then permanently fixed by a second crosslinkingstep to give a liquid single crystal elastomer.

Polymer gels comprising linear or crosslinked polymers can be obtainede.g. from polymers comprising the inventive discotic compounds by mixingthese polymers with low molecular weight liquid crystal (LMW-LC)compounds, or by polymerizing the inventive discotic compounds asdescribed above and below in the presence of LMW-LC compounds. Inparticular, polymer gels can be prepared by in-situ polymerization ofmixtures comprising inventive polymerizable discotic compounds andLMW-LC compounds.

The inventive discotic liquid crystalline compounds of formula I and IIas well as liquid crystalline materials with columnar phases obtainablefrom or comprising these compounds, such as liquid crystalline media,liquid crystalline polymers, elastomers, polymer gels and polymernetworks, can be used in various applications, like those mentionedabove in the paragraphs discussing prior art.

For example, these materials are suitable for liquid crystal displays,optical elements like polarizers, compensators or colour filters,chemical sensors, charge transport materials, optical storage media,nonlinear optics, decorative pigments, adhesives or synthetic resinswith anisotropic mechanical properties.

In particular, inventive compounds comprising polar groups, like CN orhalogen, can be switched between different states in an electric fieldand are thus suitable for electrooptical applications.

Inventive compounds comprising one or more chiral groups can be used aschiral dopants, in ferroelectric media and in nonlinear optics.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent The following examples are, therefore, to beconstrued as merely illustrative and not limitative of the remainder ofthe disclosure in any way whatsoever.

In the foregoing and in the following examples, unless otherwiseindicated, all temperatures are set forth uncorrected in degrees Celsiusand all parts and percentages are by weight.

The mesophase behaviour of the compounds prepared in the followingexamples, unless otherwise indicated, has been investigated and thephase transition temperatures determined by polarization microscopyand/or differential scanning calorimetry (DSC).

The following abbreviations are used to illustrate the phase behaviourof the compounds: G=glassy; K=crystalline; D=columnar discotic;I=isotropic. The numbers between these symbols indicate the phasetransition temperatures in degree Celsius. Numbers in brackets indicatea monotropic phase transition, i.e. a transition that is observed onlyupon cooling, unless otherwise indicated.

COMPARISON EXAMPLE

The efficiencies of PCC and VOF₃ as oxidative agent in theintramolecular cyclisation reaction of tetra-, penta- andhexamethoxycyanostilbenes have been compared experimentally. Thesynthesis of the cyanostilbenes is described below. The results aredepicted in table 1.

with R¹ and R⁶ denoting H or OCH₃.

The compounds (Ia-c) have been prepared as follows:

Ia) 2,3-Bis-(3,4Dimethoxy-phenyl)-acrylonitrile (Procedure A)

(R¹═R⁶=H)

To a stirred solution of 3,4-dimethoxybenzaldehyde (1.66 g, 100 mmol)and 3,4-dimethoxyphenyl-acetonitrile (1.77 g, 10 mmol) in 50 ml ofabsolute ethanol, cooled at 0° C. and maintained under nitrogenatmosphere, sodium ethylate (30 mmol) was portionwise added (10portions, 1 portion/2 min). After complete addition and stirring forfurther 6 h at room temperature the reaction mixture was cooled to 0° C.and a yellow precipitate occurs. This precipitate was filtered off,washed with ethanol (100 ml) and dried under reduced pressure. Thisafford the desired stilbene as yellow powder (yield 3 g, 92%).

Ib) 2-(3,4-Dimethoxy-phenyl)-3-(2,3,4-trimethoxy-phenyl)-acrylonitrile

(R¹=OCH₃, R⁶=H)

Following the Procedure A, the reaction was performed with 1.96 g of2,3,4-trimethoxybenzaldehyde (10 mmol) and 1.77 g3,4-dimethoxyphenyl-acetonitrile (10 mmol), affording2-(3,4-dimethoxy-phenyl)-3-(2,3,4-trimethoxy-phenyl)-acrylonitrile asyellow powder (yield 3.2 g, 90%).

Ic) 2,3-Bis-(2,3,4-Trimethoxy-phenyl)-acrylonitrile

(R¹═R⁶=OCH₃)

2,3,4-Trimethoxyphenyl-acetonitrile

Phosphortribromide (6.83 g, 25.22 mmol) was added dropwise to a stirredsolution of 2,3,4-trimethoxybenzyl alcohol (10 g, 54.44 mmol) indichloromethane (100 ml), cooled at 0° C. After 30 min of vigorousstirring, the reaction mixture was slowly quenched with 100 g ofice-water. The dichloromethane layer was separated and the aqueous layerwas further extracted with dichloromethane (2×100 ml). The combinedextracts were twice washed with a saturated solution of sodium chloride(2×150 ml). The organic solution was dried over magnesium sulphate andevaporated to give 10 g (yield 76%) of the benzylbromide 2 as acolourless oil. As soon as isolated, the benzyl bromide compound wasdirectly used for the next step. In fact the compound degradated afterone night even at +4° C. The obtained1-bromomethyl-2,3,4-trimethoxybenzene oil was treated with KCN (6.52 g,100 mmol) in dry DMF (30 ml), at 0° C. and under nitrogen atmosphere.The obtained mixture was stirred for 3 g at 0° C. and 1 h at 60° C. Thecooled reaction mixture was poured into water (80 ml) and extracted withdiethylether (3×150 ml). The crude benzylcyanid was chromatographed onsilica (diethylether/petroleumether: 1/3) to give2,3,4-trimethoxyphenyl-acetonitrile as a white crystalline material(Yield: 6.8 g; 86%).

2,3-Bis-(2,3,4-trimethoxy-phenyl)-acrylonitrile

Following the Procedure A, the reaction was performed with 1.96 g of2,3,4-trimethoxybenzaldehyde (10 mmol) and 2.07 g of2,3,4-trimethoxyphenyl-acetonitrile (10 mmol), affording2,3-bis-(2,3,4-trimethoxy-phenyl)-acrylonitrile as yellow powder (yield3.6 g, 93%).

The transformation of the cyanostrilbenes (Ia-c) into the phenanthrenes(IIa-c) by oxidative cyclisation is described below with PCC asoxidative agent. The cyclisation of (Ia-c) with VOF₃ as oxidative agentwas carried out in the same way, with the difference being that insteadof PCC VOF₃ was added in a molar amount twice as much as that of PCC.

IIa) 2,3,6,7-Tetramethoxy-phenanthrene-9-carbonitrile (Procedure B)

2,3-Bis-(3,4-dimethoxy-phenyl)-acrylonitile (1.83 g, 5.63 mmol) wasdissolved in absolute dichloromethane (100 ml) and the obtained solutionwas cooled to 0° C. and maintained under nitrogen atmosphere. Borontrifluoride etherate (1.76 g, 12.39 mmol) was dropwise added (within 15min) to the reaction mixture which was stirred for further 15 min at 0°C. At this temperature, pyridinium chlorochromate (PCC) (2.43 g, 11.26mmol), was portionwise added (10 portions, 1 portion/min) to thereaction mixture which turned green-brown. After complete addition ofPCC, the reaction mixture was stirred for further 10 min, poured intowater (200 ml), and extracted with dichloromethane (2×200 ml). Thecombined organic extracts were dried over magnesium sulphate andevaporated under reduced pressure. The obtained brown residue waschromatographed on silica (CH₂Cl₂). This afford a yellow material whichwas further purified by crystallisation in ethanol/dichloromethane: 9/1to give 2,3,6,7-tetramethoxy-phenanthrene-9-carbonitrile as white powder(yield 1.75 g, 96%).

IIb) 1,2,3,6,7-Pentamethoxy-phenanthrene-9-carbonitrile

Following the Procedure B, the reaction was performed with 1.78 g of2-(3,4-dimethoxy-phenyl)-3-(2,3,4-trimethoxy-phenyl)-acrylonitrile (5mmol), boron trifluoride ehterate (1.56 g, 11 mmol) and PCC (2.15 g, 10mmol), 1,2,3,6,7-pentamethoxy-phenanthrene-9-carbonitrile as whitepowder after crystallisation in EtOH/CH2Cl2:19/1 (yield 1.6 g, 90%).

IIc) 1,2,3,6,7,8-Hexanethoxy-phenanthrene-9-carbonitrile

Following the Procedure B, the reaction was performed with 1.93 g of2,3-Bis-(2,3,4-trimethoxy-phenal)-acrylonitrile (5 mmol), borontrifluoride etherate (1.56 g, 11 mmol) and PCC (2.15 g, 10 mmol),affording 1,2,3,6,7,8-hexamethoxy-phenanthrene-9-carbonitrile as whitecrystalline material after crystallisation in ethanol (yield 1.65 g,87%).

Table 1 shows the results of the comparative experiment in which eitherPCC or VOF₃ were used as oxidative agent in the preparation of thephenanthrenes IIa-c.

TABLE 1 No. R¹ R⁶ VOF₃ PCC IIa H H 85% 96% IIb OCH₃ H 50-55% 90% IIcOCH₃ OCH₃ 32-54% 87% reaction time 10-15 min  5 min < stability <decomposition

From table 1 it can easily be recognized that PCC is a more efficientoxidative agent than VOF₃, in particular when increasing the number ofsubstituents on the aromatic rings of the cyanostilbenes Ia-c. It canalso be seen that in the case of VOF₃ it is not possible to improve theyield by increasing the reaction time, since decomposition of thephenanthrene occurs.

EXAMPLE 1

1,2,3,6,7-Pentakis-heptyloxy-phenanthrene-9-carbonitrile (1) has beenprepared as follows:

Under nitrogen atmosphere, a solution of1,2,3,6,7-Pentamethoxy-phenanthrene-9-carbonitrile (0.75 g, 2.12 mmol)in CH₂Cl₂ (10 ml) was cooled to −76° C. and treated by a dropwiseaddition of 1M CH₂Cl₂ solution of BBr₃ (14 ml). After complete addition(15-20 min), the reaction mixture was stirred at room temperature for 30min and heated at reflux during 12 h. After being cooled to 0° C. thereaction mixture was gently treated with 2 ml of methanol (dropwiseaddition), poured into 30 g of ice-water and stirred for further 20 minat room temperature. The obtained mixture was saturated with NaCl andextracted with diethylether (5×60 ml). The combined organic extractswere washed with 100 ml of saturated NaCl solution, dried over magnesiumsulphate and evaporated under reduced pressure to afford thepentahydroxy-phenanthrene as slightly yellow crystalline material. Itwas then dissolved in dry DMF (5 ml) containing 2.40 g (10.60 mmol) of1-iodo heptane. To this solution, maintained under nitrogen atmosphereand stirred at room temperature, potassium carbonate (1.46 g, 10.60mmol) was added and the obtained mixture was stirred at 80° C.overnight. The cooled reaction mixture was gently poured into HCl 3N (30ml) and extracted with diethylether (3×50 ml). The combined organicextracts were washed with 80 ml of saturated NaCl solution, dried overmagnesium sulphate and evaporated under reduced pressure. The obtainedoily residue was chromatographed on silica(dichloromethane/petroleumether: 1/1) to give1,2,3,6,7-pentakis-heptyloxy-phenanthrene-9-carbonitrile as a whiteliquid-crystalline material (Yield: 0.84 g; 51%).

Compound (1) exhibits an enantiotropic columnar discotic phase and showsthe phase behaviour K-28 D 66.8 I.

The columnar discotic phase of compound (1) was investigated by X-rayexperiments. FIGS. 1A and 1B show the X-ray diffraction pattern of twosamples of compound (1) in its columnar discotic phase at roomtemperature, with FIG. 1A relating to an unoriented sample that exhibitsa polydomain structure, and FIG. 1B relating to a sample that exhibits amonodomain structure after it was sheared uniaxially.

The incident X-ray beam is perpendicular to the surface of the detectorand to the shear direction, the latter of which is corresponding to thevertical of FIGS. 1A and 1B. In FIG. 1A and 1B two reflections areshown: The wide angle reflection (a) is attributed to the intracolumnardisk spacing while the small angle reflection (b) is due to theintermolecular disk spacing.

For the polydomain sample, the distribution of the liquid crystallinedirector is isotropic, corresponding to a homogeneous azimuthaldistribution of the X-ray intensities as depicted in FIG. 1A.

For the sheared monodomain sample, the distribution of the director isanisotropic, corresponding to sharp maxima in the azimuthal distributionof the intensities as depicted in FIG. 1B. Of these, the wide anglereflection maxima (a) are perpendicular to the shear axis, whereas thesmall angle maxima (b) are parallel to the shear axis.

These results clearly demonstrate that the columns of the discotic phasein compound (1) can be oriented macrosopically parallel to the shearaxis with a high quality of alignment.

The following compounds have been prepared analoguously

R¹ R² R³ R⁴ R⁵ Phase Behaviour OC₄H₉ OC₄H₉ OC₄H₉ OC₄H₉ OC₄H₉ K (30 D 77)81 I 2-MB 2-MB 2-MB OC₇H₁₅ OC₇H₁₅ K 77 D 86.6 I 2-MB = 2-methylbutyloxy

EXAMPLE 2a

The compound6,7-Bis-heptyloxy-3,4-bis-[(S)-2-methyl-butoxy]-2-(pent-4-enyloxy)-phenanthrene-9-carbonitrile(2) carrying a polymerizable reactive group has been prepared asfollows:

(S)-2-Methyl-butyl p-Toluenesulphonate

To a ice-cooled solution of p-toluenesulphonyl chloride (9.53 g, 50mmol), (S)-2-methylbutan-1-ol (4.41 g, 50 mmol) in absolutedichloromethane (200 ml), triethylamine (84 ml) was dropwise added.After complete addition and stirring for further 6 h at roomtemperature, the reaction mixture was poured into water (150 ml), theorganic layer was separated and the aqueous phase was further extractedwith dichloromethane (2×200 ml). The combined organic extracts werewashed with HCl 1N (2×200 ml), with saturated NaCl solution (2×200 ml),dried over magnesium sulphate and evaporated under reduced pressure. Theobtained slightly yellow oil was chromatographed on silica(diethylether/petroleumether: 1/3) to give (s)-2-methyl-butylp-toluenesulphonate as a colourless oil (Yield: 10.0 g, 89%).

Tris-1,2,3-[(S)-2-Methyl-butoxy]-benzene

Under nitrogen atmosphere, a mixture of pyrogallol (1.26 g, 10 mmol),(S)-2-methylbutyl p-toluenesulphonate (8 g, 33 mmol) and potassiumcarbonate (5.53 g, 40 mmol) in dry DMF (20 ml) was stirred at 100° C.for 24 h. The cooled reaction mixture was gently poured into HCl 3N (60ml) and extracted with diethylether (3×100 ml). The combined organicextracts were washed with 150 ml of saturated NaCl solution, dried overmagnesium sulphate and evaporated under reduced pressure. The obtainedoily residue was chromatographed on silica(dichloromethane/petroleumether: 1/1) to givetris-1,2,3-[(S)-2-methyl-butoxy]-benzene as a transparent oil (Yield:2.4 g, 71%).

Tris-2,3,4-[(S)-2-Methyl-butoxy]-benzaldehyde

To a cooled (ice-water +10° C.) mixture oftris-1,2,3-[(S)-2-methyl-butoxy]-benzene (2 g, 6 mmol) andN-methylformanilide (1.62 g, 12 mmol), phosphorus oxychloride (11 g, 7.2mmol) was added dropwise. After complete addition (10 min), the reactionmixture was stirred at room temperature for 2 h and at 60° C. for 1 h.To the cooled reaction mixture, 50 g of ice were added followed by slowaddition of 5N NaOH solution until a pH of 6 was reached. This mixturewas extracted twice with 150 ml of diethylether and the combined organicextracts were washed with 100 ml of HCl 3N and with 150 ml of saturatedNaCl solution. The organic phase was dried over magnesium sulphate andevaporated under reduced pressure to afford a oily residue which waschromatographed on silica (diethylether/petroleumether: 1/3) to givetris-1,2,3-[(S)-2-methyl-butoxy]-benzaldehyde as a slightly yellow oil(Yield: 1.7 g, 78%).

2-Hydroxy-3,4-bis-[(S)-2-methyl-butoxy]-benzaldehyde

Tris-2,3,4-[(S)-2-methyl-butoxy]benzaldehyde (1.2 g, 3.3 mmol) isdissolved in CH₂Cl₂ (30 ml) and the obtained solution was cooled at −76°C. (acetone-dry ice bath) and maintained under nitrogen atmosphere. Asolution of boron tribromide (0.32 ml, 3.3 mmol) in CH₂Cl₂ (10 ml) wasadded dropwise to the stirred solution. When the addition was complete(1 h), the reaction mixture was stirred for 4 h at −76° C. The reactionmixture was then hydrolyzed by careful shaking with 30 g of ice-waterwith continuous stirring for 30 min. The obtained brownish mixture wasextracted with 3×50 ml of diethylether and the combined organic extractswere washed with saturated NaCl solution (2×50 ml), dried over magnesiumsulphate and evaporated to dryness. The obtained brown residue waschromatographed on silica (diethylether/petroleumether: 1/3) to give2-hydroxy-3,4-bis-[(S)-2-methyl-butoxy]-benzaldehyde as a slightly redoil (Yield: 0.76 g, 78%).

3,4-Bis-[(S)-2-Methyl-butoxy]-2-(pent-4-enyloxy)-benzaldehyde

Under nitrogen atmosphere, a mixture of2-hydroxy-3,4-bis-[(S)-2-methyl-butoxy]-benzaldehyde (0.74 9, 2.51mmol), 5-bromo-1-pentene (0.45 g, 3.02 mmol) and potassium carbonate(0.41 g, 3 mmol) in dry DMF (5 ml) was stirred at 80° C. for 3 h. Thecooled reaction mixture was gently poured into HCl 3N (15 ml) andextracted with diethylether (3×20 ml). The combined organic extracts arewashed with 30 ml of saturated NaCl solution, dried over magnesiumsulphate and evaporated under reduced pressure. The obtained oilyresidue was chromatographed on silica (diethylether/petroleumether: 1/3)to give 3,4-bis-[(S)-2-methyl-butoxy]-2-(pent-4-enyloxy)-benzaldehyde asa slightly yellow oil (Yield: 0.82 g, 90%).

(3,4-Dihydroxy-phenyl)-acetonitrile

3,4-Dimethoxy-phenyl)-acetonitrile (8.86 g, 50 mmol) was dissolved inCH₂Cl₂ (200 ml) and the obtained solution was cooled at −76° C.(acetone-dry ice bath) and maintained under nitrogen atmosphere. Asolution of boron tribromide (11.56 ml, 120 mmol) in CH₂Cl₂ (120 ml) wasadded dropwise to the stirred solution. As the solution of borontribromide was added, a white precipitate was formed. When the additionwas complete (30 min), the reaction mixture was allowed to attain roomtemperature overnight with stirring. The reaction mixture was thenhydrolyzed by careful shaking with 200 g of ice-water, thusprecipitating a white solid which was dissolved by the addition of 800ml of diethylether. The organic layer was separated and the aqueouslayer was saturated with NaCl and further extracted with 3×200 ml ofdiethylether. The combined organic extracts were washed with saturatedNaCl solution (2×300 ml), dried over magnesium sulphate and evaporatedto dryness to afford (3,4-dihydroxy-phenyl)-acetonitrile as white solidwith a pinkish tint (Yield: 6.9 g, 92%).

(3,4-bis-Heptyloxy-phenyl)-acetonitrile

Under nitrogen atmosphere, a mixture of(3,4-Dihydroxy-phenyl)-acetonitrile (1.49 g, 10 mmol) 1-iodo-heptane(4.97 g, 22 mmol) and potassium carbonate (2.76 g, 20 mmol) in dry DMF(20 ml) was stirred at 70° C. for 6 h. The cooled reaction mixture wasgently poured in HCl 3N (80 ml) and extracted with diethylether (3×150ml). The combined organic extracts were washed with 150 ml of saturatedNaCl solution, dried over magnesium sulphate and evaporated underreduced pressure. The obtained yellow oily residue was chromatographedon silica (diethylether/petroleumether: 1/2) to afford(3,4-bis-heptyloxy-phenyl)-acetonitrile as slightly yellow oil whichsolidified upon standing (Yield: 2.6 g, 75%).

2(3,4-bis-Heptyloxy-phenyl)-3-[3,4-bis-((S)-2-methyl-butoxy)-2-(pent-4enyloxy))-phenyl]-acrylonitrile

To a stirred solution of3,4-Bis-[(S)-2-methyl-butoxyl]-2-(pent-4-enyloxy)-benzaldehyde (0.725 g,2 mmol) and (3,4-Bis-heptyloxy-phenyl)-acetonitrile (0.691 g, 2 mmol) in10 ml of absolute ethanol, cooled at 0° C. and maintained under nitrogenatmosphere, sodium ethylate (0.408 g, 6 mmol) was portionwise added (10portions, 1 portion/2 min). After complete addition and stirring forfurther 12 h at room temperature the reaction mixture was poured into 30ml of water and extracted with diethylether (3×50 ml). The combinedorganic extracts were washed with 60 ml of saturated NaCl solution,dried over magnesium sulphate and evaporated under reduced pressure. Theobtained yellow oily residue was chromatographed on silica(diethylether/petroleumether: 1/3) to afford(3,4-bis-heptyloxy-phenyl)-acetonitrile as a slightly yellow oil whichsolidified upon standing (Yield: 1.2 g, 88%).

6,7-bis-Heptyloxy3,4-bis-[(S)-2-methyl-butoxy]-2-(pent-4-enyloxy)-phenanthrene-9-carbonitrile

2-(3,4-Bis-heptyloxy-phenyl)-3-[3,4-bis((S)-2-methyl-butoxy)-2-(pent-4-enyloxy))-phenyl]-acrylonitrile(1.03 g, 1.51 mmol) was dissolved in absolute dichloromethane (20 ml)and the obtained solution was cooled to 0° C. and maintained undernitrogen atmosphere. A solution of boron trifluoride etherate (0.47 g,3.32 mmol) in dichloromethane (3 ml) was dropwise added (within 15 min)to the reaction mixture which was stirred for further 15 min at 0° C. Atthis temperature, pyridiniumchlorochromate (PCC) (0.65 g, 3.02 mmol) wasportionwise added (10 portions, 1 portion/min) to the reaction mixturewhich turned dark-green. After complete addition of PCC, the reactionmixture was stirred for further 10 min at room temperature, poured intowater (20 ml), and extracted with dichloromethane (2×20 ml). Thecombined organic extracts were dried over magnesium sulphate andevaporated under reduced pressure. The obtained brown residue waschromatographed on silica (diethylether/petroleumether: 1/3) to affordthe titled phenanthrene as orange-yellow pasty residue. In order toremove this coloration the above residue was filtered through a shortcolumn of neutral alumina (diethylether/petroleumether: 1/6). This gavethe desired phenanthrene as white liquid-crystalline material (Yield:0.91 g, 88%)

Compound (2) exhibits a monotropic columnar discotic phase and shows thephase behaviour K 66.5 (D 62.6) I.

The following compounds comprising a polymerizable reactive group havebeen prepared analoguously

(2a-f)

No. R¹ R² R³ R⁴ R⁵ Phase Behaviour 2a 11-en OC₅H₁₁ OC₅H₁₁ OC₇H₁₅ OC₇H₁₅D 33.3 I 2b 11-en OC₆H₁₃ OC₆H₁₃ OC₆H₁₃ OC₆H₁₃ K 30.8 (D 28) I 2c 5-enOC₆H₁₃ OC₆H₁₃ OC₆H₁₃ OC₆H₁₃ K 52.3 (−13.4) D 67 I 2d 6-en OC₆H₁₃ OC₆H₁₃OC₆H₁₃ OC₆H₁₃ K 51.4 (−16.7) D 67.5 I 2e 11-en OC₇H₁₅ OC₇H₁₅ 11-en 11-enK 11.9 (−25.4) D 31.3 I 2f 11-en OC₆H₁₃ OC₆H₁₃ 11-en 11-en K 24 I 11-en= undec-10-enoxy, 6-en = hex-5-enoxy, 5-en = pent-4-enoxy

EXAMPLE 2b

The electrooptic behaviour of compound (2c) was investigated. A sampleof compound (2c) was put into a cell consisting of two glass platesseparated by glass spacers at a distance of 10 μm and partially coatedby a conductive layer of indium tin oxide (ITO). The samplespontaneously aligned homeotropically. Then a low frequency AC electricfield (1 Hz) was applied to the cell.

FIGS. 2A and 2B depict the sample between crossed nicol polarizers uponapplication an electric field of 4 V/μm (FIG. 2A) and 10 V/μm (FIG. 2B)respectively. The right sides of FIGS. 2A and 2B show the sample betweenthe ITO-coated, conductive parts of the glass plates, the left sidesshow the sample between the non-conductive parts of the glass plates.

Upon application of an electric field of 4 V/μm, the sample switchedbetween the initial homeotropic orientation and a highly bright state(FIG. 2A). When the electric field was increased to 10 V/μm, thebirefringence of the sample increased to yield a pseudo focal-conictexture (FIG. 2B), which is characteristic for columnar mesophases.

At the higher field of 10 V/μm, the switching of the sample in the slowAC field ceased visually and the initial homeotropic could only berecovered by heating the sample to the isotropic phase, followed byrecooling to the discotic phase.

EXAMPLE 3a

The elastomers (3a) to (3h) have been prepared from the monomers (2b) to(2d) and the crosslinkers (2e), (2f) and (v) shown in table 2 by thefollowing methods which is described in detail for elastomer (3c):

60.12 mg (1 mmol of SiH groups) of poly[oxo(methylsilylene)], 584.8 mg(0.85 mmol) of mesogen (2c(, 49.82 mg (0.05 mmol) of cross-linker (2e)and 5 μl of platinum catalyst SLM 85006 (Wacker Chemie Burghausen) weredissolved in 1 ml of absolute toluene and the obtained solution wasfiltered using a 0.5 mm Millipore filter and filled into a centrifugecell with a diameter of 5 cm and a height of 1 cm, excluding dustparticles. To avoid tack, the inner wall of the cell is covered with ateflon film. The reaction was carried out under centrifugation (4000rpm) at 60° C. for 2 h. Thereafter the whole cell is cooled to roomtemperature and the swollen elastomer is carefully removed from thecell. The swollen elastomer is fixed at one end with an clamp anduniaxially strained by a stress applied from the other end of the film.It was then annealed for 24 h at room temperature, to complete thecross-linking reaction. This leads to a transparent liquid-crystallinesample.

The polydomain sample is prepared under similar conditions, however,without load during the deswelling process.

Elastomers (3a,b) and (3d-h) have been prepared analoguously.

TABLE 2 n m No.

9 3 4 — — — 2b 2c 2d

— — 7 6 2e 2f

— — v

The elastomers exhibit the following phase behaviour

Reaction ΔH No. Monomer Crosslinker Time (h) Phase Behaviour (kJ/mol) 3a2b v 1.5 G-23 I — 3b 2b 2e 1.5 G-17 I — 3c 2c 2e 24 G-19 D 50 I 1.2 3d2c 2e 72 G-24 D 48 I 2.2 3e 2c v 72 G-31 D 52 I 1.1 3f 2d v 1 G-14 I —3g 2d v 48 G-18 I — 3h 2d 2f 1 G-8 I —

The elastomers (3c) to (3e) prepared from monomer (2c) with a pentylspacer exhibit a broad columnar discotic phase independently from thetype of crosslinker used, whereas in the elastomers prepared frommonomer (2b) and (2d) with a hexyl and undecenyl spacer the mesophase issuppressed below the glass transition.

This is in accordance with the phase behaviour of the correspondingmonomers of example 2, wherein compound (2c) with a short spacer has abroader discotic phase and a higher clearing point than compound (2b)with a long spacer.

Furthermore, in the case of monomer (2c) a longer hydrosilylationreaction time was required to form the networks (3c) to (3e). Incontrast to that, in the case of monomer (2d) the network was obtainedwithin 1 h only and a prolonged reaction time had no further effect, ascan be taken from the comparison of (3f) and (3g).

Thus, an increase of the spacer length of only one CH₂ group has aconsiderable effect on the stability of the columnar mesophase of theelastomer and also on the efficiency of the polymerization reaction.

EXAMPLE 3b

The anisotropy of the networks of example 3a was investigated byswelling experiments. Isotropic networks swell identically in the threedimensions, whereas anisotropic networks obtained by uniaxial stressswell less in the direction of the stress axis than in the directionperpendicular to the stress axis.

The results of the swelling experiments of poly- and monodomainelastomers (3c) and (3e) in toluene are outlined in table 3. The samples(I) and (II) are unstrained polydomain networks, whereas (III) and (IV)have been strained during their synthesis as described above. Sample (V)has been strained in the isotropic state and recooled to the discoticliquid crystalline state.

In table 3, α_(∥) and α_(⊥) denote the swelling coefficientsrespectively parallel and perpendicular to the stress axis and aredefined as the ratio of the respective network dimension in the swollenand the unswollen state. The anisotropy of the network is given by theratio α_(⊥)/α_(∥). The degree of swelling q=α_(⊥)α_(∥) ² is related tothe average molar mass of the strands of the network, and is thus afunction of the cross-linking density.

TABLE 3 Sample Elastomer Stress (N · mm⁻²) α_(II) α_(⊥) α_(⊥)/α_(II) q I3c 0 1.6 1.7 1.1 4.6 II 3e 0 1.6 1.6 1.0 4.1 III 3c 0.009 1.2 2.0 1.74.8 (during synthesis) IV 3e 0.012 1.1 1.9 1.7 4.0 (during synthesis) V3e 0.011 1.1 2.0 1.8 4.4 (at isotropic state)

The data in table 3 show that the unstrained polydomain networks (I) and(II) swell isotropically, whereas the networks prepared with uniaxialstress during their synthesis (III, IV) or being strained in theisotropic state (V) swell anisotropically, as indicated by their higherswelling coefficients in the direction perpendicular to the stress axis.

EXAMPLE 3c

The columnar discotic phases of elastomers (3c) and (3e) have beenfurther investigated by X-ray experiments. The results are depicted inFIGS. 3A to 3E and FIGS. 4A to 4D.

FIGS. 3A to 3D show the X-ray diffraction pattern of two samples ofelastomer (3c) in its columnar discotic phase at room temperature, withFIG. 3A refering to a polydomain sample, and FIGS. 3B to 3D refering toa monodomain sample.

In FIGS. 3B and 3C, the incident X-ray beam is perpendicular to thesurface of the detector and to the stress direction, whereas in FIG. 3Dthe incident beam is parallel to the stress direction. The spatialrelationship between the network sample, the axis of stress a and thedirection of incidence of the X-ray beam is depicted in the FIGS. 3B to3D.

Two reflections are shown: The wide angle reflection (a) is attributedto the intracolumnar disk spacing while the small angle reflection (b)is due to the intermolecular disk spacing.

For the polydomain sample (FIG. 3A), the distribution of the liquidcrystalline director is isotropic, corresponding to a homogeneousazimuthal distribution of the X-ray intensities.

For the monodomain samples, when being viewed at perpendicular to thestress direction, the distribution of the director is anisotropic,corresponding to sharp maxima in the azimuthal distribution of theintensities (FIGS. 3B and 3C). Of these, the wide angle reflectionmaxima (a) are parallel to the stress axis and the small angle maxima(b) are perpendicular to the stress axis. This demonstrates clearly thatthe columns are macroscopically oriented parallel to the stress axis,which is in agreement with the results of the swelling experiments.

In accordance with that, in case of the incident X-ray beam beingparallel to the stress axis (FIG. 3D), although the sample is amonodomain, only the small angle reflection (b) corresponding to theintercolumnar disk spacing is observed, and the reflection pattern isisotropic, since the liquid crystal director and thus the anisotropy ofthe columnar phase are not detectable when viewing in the directionparallel to the columns.

The azimuthal intensity distribution of the diffraction pattern of thepolydomain sample (i.e. a scan across FIG. 3A in any direction) isdepicted in FIG. 3E and shows a maximum a) at an angle 2θ of 24.7°,corresponding to a molecular distance d of 3.6 Å (intracolumnarcorrelation, 11 molecules), a maximum b) at an angle of 4.7°,corresponding to a molecular distance of 17.9 Å (intercolumnarcorrelation, 9 columns), and a maximum c) at an angle of 19.7°,corresponding to a molecular distance of 10.3 Å.

FIGS. 4A and 4B show the X-ray diffraction pattern at room temperatureof two polydomain samples of elastomer (3e) that have been oriented bymechanical stress. The incident X-ray beam is perpendicular to thesurface of the detector and to the stress direction. FIG. 4A refers to asample that is strained in the discotic liquid crystalline phase. FIG.4B refers to a sample that has been strained in the isotropic state andrecooled to the discotic phase.

In both states, the director is anisotropic, corresponding to sharpmaxima in the azimuthal intensity distribution of the wide anglereflection (a) parallel and the small angle reflection (b) perpendicularto the stress axis.

The azimuthal intensity distribution of the diffraction pattern of FIG.4A is shown in FIGS. 4C and 4D, with FIG. 4C depicting the small anglereflection (i.e. a scan across FIG. 4A in horizontal direction) and FIG.4D the wide angle reflection (i.e. a scan across FIG. 4A in verticaldirection). The reflection maximum a) in FIG. 4C at an angle 2θ of5.07°, corresponding to a distance of 17.7 Å, is showing theintercolumnar correlation (14 columns). The reflection peak b) in FIG.4C at an angle 2θ of 8.6°, corresponding to a distance of 10.3 Å isshowing the hexagonal second order diffraction and indicates a hexagonallattice of the columns. The reflection maximum a) in FIG. 4D at an angle2θ of 25°, corresponding to a distance of 3.6 Å, is attributed to theintercolumnar correlation (11 molecules). It can be seen that the peaksa) in FIG. 4C and a) in FIG. 4D are perfectly separated.

These results show that the discotic columns are macroscopicallyoriented parallel to the stress axis, and are in good agreement with theresults of the swelling experiments.

EXAMPLE 4

The following compounds have been prepared

(A)

(B)

Compound No. 4a 4b 4c 4d 4e 4f Formula A A B B B B R CN CHO CN CHO7-enOH 7-enO 7-enOH = —CH(OH)—(CH₂)₄—CH═CH₂, 7-enO = —CO—(CH₂)₄—CH═CH₂

Compounds (4a) and (4c) wherein R is CN have been prepared as describedin examples 1 and 2a. The compounds (4d) to (4f) have been prepared fromcompound (4c) by transformation of the cyano group as described below.Compound (4b) was obtained in an analoguous manner from compound (4a).

1,2,3-Tributoxy-6,7-bis-pentyloxy-phenanthrene-9-carbaldehyde (4d)

A solution of diisobuthylaluminohydride (1M in toluene, 10 ml, 10 mmol)was added dropwise, under a nitrogen atmosphere to a solution of1,2,3-tributoxy-6,7-bis-pentyloxy-phenanthrene-9-carbonitrile (2.96 g, 5mmol) in dry toluene (50 ml), cooled at −76° C.

After complete addition of the hydride (1 h), the obtained yellowsolution was stirred at −76° C. for 2 h, then at room temperature for 3h. The reaction mixture was then cooled at 0° C and 10 ml of methanolwere added followed by dropwise addition of 150 ml of cold 5N sulfuricacid. After stirring for 5 h at room temperature, the yellow-orangereaction mixture was extracted with diethylether (4×200 ml) and thecombined ether extracts were washed with saturated NaHCO₃ solution (300ml), with saturated NaCl solution (2×200 ml), dried over magnesiumsulphate and evaporated to dryness. The obtained yellow-orange oilyresidue was chromatographed on silica (dichloromethane/petroleumether:2/1) to afford1,2,3-tributoxy-6,7-bis-pentyloxy-phenanthrene-9-carbaldehyde as yellowliquid-crystalline material which crystallised upon standing (Yield 2.43g, 82%).

1-(1,2,3-Tributoxy-6,7-bis-pentyloxy-phenanthren-9-yl)-hept-6-en-1-ol(4e)

To a suspension of magnesium (98 mg, 4 mmol) in dry THF (8 ml), asolution of 6-bromo-1-hexene (0.65 9, 4 mmol) in dry THF (2 ml) wasadded under a nitrogen atmosphere and the obtained reaction mixture wasstirred at room temperature until complete consummation of the metal.This mixture was then added dropwise under a nitrogen atmosphere to asolution of1,2,3-tirbutoxy-6,7-bis-pentyloxy-phenanthrene-9-carbaldehyde (2 g, 3.36mmol) in dry toluene (20 ml) cooled at 0° C. After complete addition ofthe grignard reagent (15 min) the reaction mixture was stirred for 1 hat 0° C. then quenched with 50 ml of HCl 1N. The obtained mixture wasextracted with diethylether (3×80 ml) and the combined ether extractswere washed with saturated NaCl solution (2×80 ml), dried over magnesiumsulphate and evaporated to dryness. The obtained oily residue waschromatographed on silica (dichloromethane) to afford1-(1,2,3-tributoxy-6,7-bis-pentyloxy-phenanthren-9-yl)-hept-6-en-1-ol ascolourless oil which crystallised upon standing (Yield 1.9 g, 83%).

1-(1,2,3-Tributoxy-6,7-bis-pentyloxy-phenanthren-9-yl)-hept-6-en-1-one(4f)

To a suspension of 1.4 mmol/g of pyridinium chlorochromate on basicalumina (3.2 g, 4.5 mmol of PCC) in hexane (20 ml) a solution of1-(1,2,3-tributoxy-6,7-bis-pentyloxy-phenanthren-9-yl)-hept-6-en-1-ol(1.02 g, 1.5 mmol) in hexane (30 ml) was added under a nitrogenatmosphere and the obtained mixture was stirred at room temperature for5 h (the original orange coloration of the suspension turned brown). Thereaction mixture was then filtered and the black alumina residue wasfurther washed with 100 ml of hexane. After evaporation of hexane theobtained slightly orange residue was filtered over short silica-gelcolumn (diethylether(hexane: 1/1) to afford1-(1,2,3-tributoxy-,6,7-bis-pentyloxy-phenanthren-9-yl)-hept-6-en-1-oneas yellow liquid-crystalline material (Yield 0.92 g, 91%).

The compounds show the following phase behaviour

No. Formula R Phase Behaviour ΔH (kJ/mol) 4a A CN K 52.3 (−13.4) D 67 I2.2 4b A CHO K 38 D 44.5 I 3.1 4c B CN K (30 D 77) 81 I — 4d B CHO K49.5 (−25.3) D 63.5 I 3.86 4e B 7-enOH K 50.7 I — 4f B 7-enO K 21.5(20.6) D 66.2 I 7.1 7-enOH = —CH(OH)—(CH₂)₄—CH═CH₂, 7-enO =—CO—(CH₂)₄—CH═CH₂

In case of compounds of formula A, the cyano-substituted compound (4a)exhibits a higher stability of the discotic phase, with a higherclearing point than the corresponding aldehyde (4b).

In case of compounds of formula B with shorter alkoxy substituents, thealdehyde compound (4d) has a higher stability of the discotic phase,whereas the cyano compound (4c) shows even only a monotropic phase. Thehomologue (4e) with a hydroxy-substituted alkenyl group shows nomesophase at all, while the corresponding ketone (4f) exhibits adiscotic phase with the highest stability of all compounds of example 4.

This indicates that discotic phenanthrenes of formula II wherein W is anelectron withdrawing group show good discotic phase behaviour.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various conditions andusages.

What is claimed is:
 1. A process of preparing a discotic liquidcrystalline compound by intramolecular oxidative cyclisation of a diarylcompound in an organic solvent in the presence of a strong acid, whereinan oxidative agent comprising a chrom(VI)oxide derivative is used.
 2. Aprocess according to claim 1 of preparing a discotic liquid crystallinecompound of formula I

by intramolecular oxidative cyclisation of a diaryl compound of formulaIa

wherein A is an aliphatic or aromatic five- or six-membered ring, Y is—CH₂—, —NH—, —CH═CW—, —CO—, —COO—, or a radical >CH—CH< or >C═C< that ispart of a mono- or bicyclic group comprising one or two condensatedfive- or six-membered aromatic or aliphatic rings, each of which maycomprise one or more hetero atoms and may be unsubstituted, mono- orpolysubstituted by R¹, W is halogen, a dipolar group selected from CN,NO₂, SO₂CH₃, SOCH₃, SOCF₃, SOOCH₃, SOOCF₃ or COR¹, or has one of themeanings of R¹, R¹ to R⁶ are in each case independently H,straight-chain or branched alkyl with 1 to 15 C atoms which may beunsubstituted, mono- or polysubstituted by halogen or CN, it being alsopossible for one or more non-adjacent CH₂ groups to be replaced, in eachcase independently from one another, by —O—, —S—, —NH—, —N(CH₃)—,—CH(OH)—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CH═CH— or —C≡C—in such a manner that oxygen atoms are not linked directly to oneanother, or alternatively one or more of R¹ to R⁶ are denotingP—(Sp—X)_(n)—, P is a polymerizable group, Sp is a spacer group having 1to 15 C atoms, X is group selected from —O—, —S—, —CO—, —COO—, —OCO—,—OCO—O—, —S—CO—, —CO—S— or a single bond, and n is 0 or
 1. 3. A processaccording to claim 1, wherein the oxidative agent is a pyridiniumcomplex or pyridinium complex salt of a chrom(VI) oxide derivative.
 4. Aprocess according to claim 1, wherein boron trifluoride etherate ortrifluoroacetic acid is used as strong acid in the intramolecularcyclisation reaction.
 5. A process according to claim 1 of preparing adiscotic liquid crystalline phenanthrene derivative of formula II

by intramolecular oxidative cyclisation of a stilbene derivative offormula IIa

W is halogen, a dipolar group selected from CN, NO₂, SO₂CH₃, SOCH₃,SO₂CF₃, SOOCH₃, SOOCF₃ or COR¹, or has one of the meanings of R¹, R¹ toR⁶ are in each case independently H, straight-chain or branched alkylwith 1 to 15 C atoms which may be unsubstituted, mono- orpolysubstituted by halogen or CN, it being also possible for one or morenon-adjacent CH₂ groups to be replaced, in each case independently fromone another, by —O—, —S—, —NH—, —N(CH₃)—, —CH(OH)—, —CO—, —COO—, —OCO—,—OCO—O—, —S—CO—, —CO—S—, —CH═CH— or —C≡C— in such a manner that oxygenatoms are not linked directly to one another, or alternatively one ormore of R¹ to R⁶ are denoting P—(Sp—X)_(n)—, P is a polymerizable group,Sp is a spacer group having 1 to 15 C atoms, X is group selected from—O—, —S—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S— or a single bond,and n is 0 or
 1. 6. A process according to claim 5, wherein W is —CN,—CHO or P—(Sp—X)_(n)—.
 7. A process according to claim 5, wherein atleast two of R¹ to R⁶ are each independently denoting straight-chain orbranched alkoxy or alkenyloxy with 1 to 12 C atoms.
 8. A process ofaccording to claim 5, wherein at least one of R¹ to R⁶ is denotingP—(Sp—X)_(n).
 9. A process according to claim 5, wherein P is a vinyl,vinyloxy, acrylate, methacrylate, chloroacrylate, epoxy or styrenegroup.
 10. A process according to claim 5 of preparing a discotic liquidcrystalline phenanthrene derivative of formula II by reacting thebenzaldehyde IIb*

with the benzylcyanide IIc*

wherein R¹* to R⁶* have one of the meanings of R¹, in the presence of abase to the cyanostilbene IIa*,

followed by intramolecular oxidative cyclisation of the cyanostilbeneIIa* in an organic solvent in the presence of pyridinium chlorochromate(PCC) and a strong acid to give the phenanthrene II*,

and optionally converting one or more of the groups R¹* to R⁶* and/orthe nitrile group of the phenanthrene II* by known methods into thedesired substituents to give a phenanthrene derivative of formula II.11. A process according to claim 10, wherein R²*, R³*, R⁴* and R⁵* areeach independently denoting straight-chain or branched alkoxy oralkenyloxy with 1 to 12 C atoms.
 12. A process of preparing compounds offormula I according to claim 2, wherein Y is —NH—, —CO—, —COO— ordenotes

wherein the phenyl ring may be unsubstituted, mono- or polysubstitutedby R¹ as defined in formula I.
 13. A discotic liquid crystallinecompound of formula I

wherein A is an aliphatic or aromatic five- or six-membered ring, Y is—CH═CW—, —CO—, —COO—, or a radical >CH—CH< or >C═C< that is part of amono- or bicyclic group comprising one or two condensed five- orsix-membered aromatic or aliphatic rings, each of which may comprise oneor more hetero atoms and may be unsubstituted, mono- or polysubstitutedby R¹, W is halogen, a dipolar group or has one of the meanings of R¹,R¹ to R⁶ are each independently H, straight-chain or branched alkyl with1 to 15 C atoms which may be unsubstituted, mono- or polysubstituted byhalogen or CN, one or more non-adjacent CH₂ groups optionally beingreplaced, in each case independently from one another, by —O—, —S—,—NH—, —N(CH₃)—, —CH(OH)—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—,—CH═CH— or —C≡C— in such a manner that oxygen atoms are not linkeddirectly to one another, or one or more of R¹ to R⁶ is P—(Sp—X)_(n)—, Pis a polymerizable group, Sp is a spacer group having 1 to 15 C atoms, Xis —O—, —S—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, or a singlebond, and n is 0 or 1, wherein at least one of R¹ to R⁶ or W isP—(Sp—X)_(n).
 14. A liquid crystalline medium with a columnar phasecomprising at least two components, at least one of which is a discoticliquid crystalline compound according to claim
 13. 15. A linear orcrosslinked liquid crystalline (co)polymer obtainable from discoticliquid crystalline compounds according to claim 13 by polymerization orpolymeranaloguous reaction.
 16. A discotic liquid crystalline compoundaccording to claim 13, wherein Y is —CH═CW— and W is as defined informula I.
 17. A discotic liquid crystalline compound according to claim13, wherein Y is >C═C< that is part of a phenylene ring which isunsubstituted, or mono- or polysubstituted by R¹ to R⁶ as defined informula I.
 18. A discotic liquid crystalline compound of formula II

wherein W is a halogen, a dipolar group or P—(Sp—X)_(n)— R¹ to R⁶ areeach independently H, straight—chain or branched alkyl with 1 to 15 Catoms which may be unsubstituted, mono- or polysubstituted by halogen orCN, it being also possible for one or ore non-adjacent CH₂ groups to bereplaced, in each case independently from one another, by —O—, —S—,—NH—, —N(CH₃)—, —CH(OH)—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—,—CH═CH— or —C≡C— in such a manner that oxygen atoms are not linkeddirectly to one another, or one or more of R¹ to R⁶ is P—(Sp—X)_(n)—, Pis a polymerizable group, Sp is a spacer group having 1 to 15 C atoms, Xis —O—, —S—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, or a singlebond, and n is 0 or
 1. 19. A discotic liquid crystalline compoundaccording to claim 16, wherein W is CN, F, Cl, CHO, COR¹ orP—(Sp—X)_(n)—.
 20. A discotic liquid crystalline compound according toclaim 13, wherein one, two or three of R¹ and R⁶ are P—(Sp—X)_(n)—. 21.A discotic liquid crystalline compound according to claim 13, wherein Pis a vinyl, vinyloxy, acrylate, methacrylate, chloroacrylate, epoxy orstyrene group.
 22. A discotic liquid crystalline compound according toclaim 13, wherein W is CN, NO₂, SO₂CH₃, SOCH₃, SOCF₃, SOOCH₃, SOOCF₃ orCOR¹.
 23. A discotic liquid crystalline compound according to claim 18,wherein W is CN, NO₂, SO₂CH₃, SOCH₃, SOCF₃, SOOCH₃, SOOCF₃ or COR¹. 24.A discotic liquid crystalline compound according to claim 18, wherein Wis CN, F, Cl, CHO, COR¹ or P—(Sp—X)_(n)—.
 25. A discotic liquidcrystalline compound according to claim 18, wherein one, two or three ofR¹ and R⁶ are P—(Sp—X)_(n)—.
 26. A discotic liquid crystalline compoundaccording to claim 18, wherein P is a vinyl, vinyloxy, acrylate,methacrylate, chloroacrylate, epoxy or styrene group.
 27. A discoticliquid crystalline compound according to claim 13, obtainable by aprocess comprising intramolecular oxidative cyclisation of a diarylcompound in an organic solvent in the presence of a strong acid, whereinan oxidative agent comprising a chrom(VI)oxide derivative is used.
 28. Adiscotic liquid crystalline compound according to claim 18, obtainableby a process comprising intramolecular oxidative cyclisation of a diarylcompound in an organic solvent in the presence of a strong acid, whereinan oxidative agent comprising a chrom(VI)oxide derivative is used.
 29. Aliquid crystal display, optical element polarizer, compensator, colorfilter, charge transport material, chemical sensor, optical storagemedia, nonlinear optic, decorative pigment, adhesive, or syntheticresin, with anisotropic mechanical properties, comprising a liquidcrystalline compound according to claim
 13. 30. A liquid crystaldisplay, optical element polarizer, compensator, color filter, chargetransport material, chemical sensor, optical storage media, nonlinearoptic, decorative pigment, adhesive, or synthetic resin, withanisotropic mechanical properties, comprising a liquid crystallinecompound according to claim
 18. 31. A liquid crystal display, opticalelement polarizer, compensator, color filter, charge transport material,chemical sensor, optical storage media, nonlinear optic, decorativepigment, adhesive, or synthetic resin, with anisotropic mechanicalproperties, comprising a liquid crystalline compound according to claim15.